10Base5 (10 Mbps, baseband, 500
meter): one of
several physical media specified by 802.3 for use in an Ethernet local area
network LAN); consists of Thickwire coaxial cable with a maximum segment length
of 500 meters
10Base2 (10 Mbps, baseband, 185
meter): one of
several physical media specified by IEEE 802.3 for use in an Ethernet local
area network LAN); consists of Thickwire coaxial cable with a maximum segment
length of 185 meters
10BaseT (10 Mbps, baseband,
unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an
Ethernet local area network (LAN); is ordinary telephone twisted pair wire
100BaseT (100 Mbps, baseband,
unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an
Ethernet local area network (LAN); referred to as Fast Ethernet because of its
higher transmission speed
AAL (ATM adaptation layer): adapts PDUs passed down from higher
layers onto ATM cells
Active hub: allows multiple devices to be wired
to a central location to share the same media and regenerate the signal; also
referred to as multiport repeaters
ADSL (asymmetric digital subscriber
line): typical form
of xDSL telephone companies offer to residences
AGP (accelerated or advanced
graphics port): a
high-speed, point-to-point channel for attaching a graphics card to a
computer’s motherboard, primarily to assist in the acceleration of 3D computer
graphics
ALU (arithmetic logic unit): a digital circuit that calculates an
arithmetic operation (e.g., addition, subtraction) and logic operations between
two numbers; the fundamental building block of the Central Processing Unit
(CPU) or a computer
AM
(amplitude modulation): a technique used for transmitting information via a radio carrier wave.
Amplitude: height of the wave at
any point in the wave
ANSI (American National
Standards Institute): a voluntary organization that coordinates the development
and use of consensus standards in the United States and represents the needs
and views of U.S. stakeholders in standardization forums around the globe
API (application
programming interface): gives programmers a formal set of routines to call on to use
underlying network services
Application layer: performs the functions
of file transfer, e-mail, etc. (see OSI Model)
Architecture: how a system is
designed; includes how the components are connected to and operate with each
other
ARP (address resolution
protocol): network layer protocol provided with TCP/IP; used to map an IP
(internet protocol) address to a MAC (media access card) address
ASCII (American Standard
Code for Information Interchange): relates a number from 0 to 255 in the binary
(base 2) form to keyboard characters
ASIC
(application-specific integrated circuit): an integrated circuit designed for a
particular use (e.g., a chip designed solely to run a cell phone)
Asynchronous
communication: describes when devices, such as computers, rely on their own
internal clocks; it provides connectivity to printers, modems, fax machines,
etc.
ATM (asynchronous transfer
mode): high
bandwidth, cell-switching technology; designed to carry many different types of
information, including voice, video, image, data, and graphics; another form of
STDM (statistical time division multiplexing)
AUI (attachment unit
interface): a 15-pin connection that provides a path between a node’s Ethernet
interface and the medium attachment unit (MAU); also known as a transceiver
AS (Autonomous system): collection of IP
networks under the control of a single entity
B (bearer) channel: carries voice, video,
image, or data traffic, depending upon the equipment and applications available
Bandwidth: expressed in a range of
frequencies using hertz as the unit of measurement; also called analog capacity
Base 2 System: binary number system,
only two discrete values (0 and 1) are possible and all numbers are a
combination of these two characters; digital signals are numbers sent in the
Base 2 system
Base 10 System: the decimal system
Baseband: describes signals and
systems whose range of frequency is measured from 0 to a maximum bandwidthor
highest signal frequency; sometimes used as a noun for a band of frequencies
starting at 0
BGP (border gateway
protocol): an interautonomous system routing protocol; a network or group of
networksunder a common administration and with common routing policies
Bit: contraction of the
expression “binary digit”; smallest unit of data in a computer
BIOS (basic input/output
system): the
firmware code run by an IBM-compatible PC when first powered on, known as “booting
up”; primary function is to prepare the machine so other software programs can
load, execute, and assume control of the PC
Bluetooth: specification that
allows mobile phones, computers, and PDAs to be connected wirelessly over short
ranges
Bps: bits per second: common
measure of data speed for computer modems and transmission carriers
BRI (basic rate
interface): an integrated services digital network configuration, usually
intended for the home and small enterprise (see also PRI)
Bricks and clicks: business that existed
pre-Internet that now uses e-commerce technology to sell on the Internet
Bridge: interprets the LAN
hardware adapter address contained in MAC and decide whether to filter or
forward the frame; does not change the frame in any way
Browsers: client applications that
access WWW servers
Building backbone: connects LANs within a
building
Bus: electrical connection
between any two components in a computer
Bus topology: system layout where
electrical signals generated by a device connected anywhere on the bus are
received by all other connected devices
Byte: the standard size of
data in a computer; 8-bits
Cache: keeps data the processor
is likely to need quickly close at hand; increases processor operation speed
CAD/CAM (computer-aided
design/computer-aided manufacturing): software used to design products such as
electronic circuit boards in computers
Campus backbone: connects building LANs
together
CAP (competitive access
provider): company that provides network links between the customer and the
IntereXchange carrier or directly to the internet service provider (ISP); CAPs
operate private networks independent of local exchange carriers
CD-R (compact disc -
recordable): special type of CD-ROM that can be written onto by any computer with
a recording drive; can only be written onto once
CD-ROM (compact disc
read-only memory): optical storage device read by lasers; can hold up to 700 megabytes
of data
CD-RW (compact disc -
rewritable): special type of CD-ROM that can be written onto by any computer with
a recording drive; can be written onto more than once
Checksum: a count of the number of
bits in a transmission unit that is included with the unit so the receiver can
check to see whether the same number of bits arrived
CIR (committed information
rate): describes
the user information transfer rate the network supports during normal network
operations
CLEC (competitive local
exchange carrier): In the US, a telecommunications provider company (also called a
carrier) that competes with other, already established carriers (the local
telephone company; e.g., GTE, Bell South).
CLI (command line
interface): allows precise control of a function, but requires remembering all
the correct commands and switches necessary for a task; used in DOS; a way of
interacting with computers
Client/server
architecture: network where some computers are dedicated clients (workstations)
and some are dedicated servers; information is centralized on the server, and
an administrator sets policies and manages it
CMOS (complementary
metal-oxide semiconductor) RAM: requires very little power; maintains
information even when the computer is off
Collision: occurs when several
network users communicate at the same time and interfere (collide) with one
another
Collision domain: logical network segment
where data packets can "collide" with one another for being sent on a
shared medium, in particular in the Ethernet networking protocol
Computer networking: a combination of
hardware and software that lets the various computers in an organization
communicate with one another
Computer operating
system (OS): special computer program that provides an environment in which other
programs can use the computer’s central processor and the attached input/output
devices
Connectivity devices: bring users of the
network into contact with one another
Constant bit rate (CBR):
transmission
that uses a set amount of network capacity on a continual basis; used when the
arrival of the information is time-sensitive
Convergence: the merging and sometimes
clashing of voice and data networks
CPE (customer premises
equipment): generally refers to telephones, DSL or cable modems, or purchased set-top
boxes for use with communication service providers’ services
CPS (cycles per second):
measure
of how frequently an alternating current changes direction; has been
replaced by the term
hertz (Hz)
CPU (Central Processing
Unit): the
brain of the computer system where calculations and decisions are
made; also referred to
as the processor
CPU Speed: how fast the CPU works
CSU (channel service
unit): provides
a loopback function for telephone company testing, and checks bipolar
signal generation
CRC (cyclic redundancy
check): method
of checking for errors in data that has been transmitted on a communications
link; a function used to
produce a Checksum against a block of data
CS (convergence
sublayer): particular protocols that are responsible for gathering and
formatting higher
layer information so it
can be processed by the lower layers
CSMA/CD (carrier sense
multiple access/collision detect): set of rules for determining how network
devices response when
two devices collide